The present invention relates to an embroidery stitch formation device for sewing machine. More specifically this invention contemplates providing an embroidery stitch formation device by adopting a lockstitch sewing machine.
In conventional embroidery machine, a chainstitch sewing machine is adopted whereby a chainstitch embroidery is formed as shown in FIG. 1 of the accompanying drawing. The sewing machine designed for this type of embroidery stitch formation is provided with a hook needle which functions to pick up a piece of chainstitch thread supplied through a looper located underneath a sewing machine bed while a piece of cord is wound with turns of bobbin thread which is also caught by the piece of chainstitch thread thereby chainstitch embroidery seams are formed.
The structure of embroidery seam formed by a chainstitch embroidery machine thus explained is illustrated in FIG. 1.
In a conventional chainstitch embroidery machine, a piece of thread for chainstitching is adopted to form a single thread chainstitch embroidery. Therefore, if a piece of chainstitch thread is inadvertently untied or come apart, for example, as by washing the embroidered fabrics or the like, the stitch formation may get loosen or be untied successively and usually a lot of skill is required for repairing the defects thereof.
In addition, as long as hook needle is used for the purpose, there may be a possibility that the hook needle tends to catch a yarn from among the woven fabrics together with a piece of chain thread during its upward motion thereby the yarn comes out of the surface of the fabrics. Naturally a smooth stitching operation may be hindered with the result than an efficient production of high grade embroidered goods may not be obtained.
It is an object of this invention to provide an embroidery stitch formation device to overcome the drawbacks heretofore mentioned by adopting a lockstitch sewing machine which is designed to form an embroidery seam which may not easily be untied or loosened wherein a piece of bobbin thread and a piece of cord which join in the formation of embroidery seam are reinforced by a lockstitch seam formed by a piece of needle thread and a piece of lockstitch bobbin thread to avoid an easy undoing of a seam.
In a conventional machine for chainstitch embroidery, as was explained heretofore and is shown in FIG. 2, a piece of cord (a) is wound with turns of a piece of bobbin thread (c) while a piece of thread (b) for chain-stitching is caught by the piece of bobbin thread (c) during the stitching process of forming an embroidery seam. While the piece of cord (a) is hanging downward in parallel with a hook needle (e), the latter (e) is shifted downward through both a piece of cloth (d) and a hole (o) provided in a table (T) to catch the piece of chainstitch thread (b) provided in a looper (f) and as soon as the piece of chainstitch thread (b) is caught by the hook needle (e) and is lifted upward through the hole (o) of the table (T) to be thrown into a predetermined position to form a chainstitch, the piece of cord (a) is wound with turns of the piece of bobbin thread (c) supplied, through a thread guide (m), from a bobbin (g) rotatably supported on a support arm (j) positioned on a rotary ring (k) in unison with the rotation thereof in a direction of an arrow as illustrated in FIG. 2, and simultaneously with the formation of chainstitch by the piece of chain-stitch thread (b) the piece of bobbin thread (c) is also caught thereby.
The bobbin (g) is mounted rotatably on the support arm (j) by means of an upright shaft (h) provided thereon. The support arm (j) is fixed horizontally to a rotary ring (k) having a rotatable gear (l). When a bulky bobbin thread (c) is wound on the bobbin (g) it may be impossible to supply an ample thread thereon because of the small capacity of the bobbin thus mounted upright on the support arm (j). Therefore, this causes a repetition of stopping the machine to supply bobbin thread thereon and entails not only a loss of time in machine operation but involves the use of an extra costly labor. This drawback may be overcome by mounting a large bobbin having a big capacity on a longer supporting arm fixedly protruding from rotary ring (k). However, this brings forth an increase of orbitual radius of the rotation when the bobbin (g) supported on the long support arm rotates around a needle bar (i) with a resultant slow rotation thereof coupled with drawbacks such as untimely and inadvertent unwinding of bobbin thread (c) due to the rotation of bobbin supported on the support arm and the centrifugal force created by the rotation of rotary ring (k) on which is mounted the long support arm.
In other words, the size of the bobbin is too small to be provided with an ample bobbin thread thereon at one time according to the conventional structure of bobbin means coupled with some difficulty of smooth unwinding of bobbin thread from the bobbin corresponding to the stitching speed of the sewing machine.
As will be explained hereinafter, suppose a lockstitch embroidery machine according to the present invention is provided with the bobbin means having the same structure as the conventional type chainstitch machine on a rotary ring the same drawback may be found.
It is another object of this invention to present bobbin means to overcome the above mentioned drawbacks by providing a longer slant arm on which is mounted a bigger bobbin slantwise and downwardly so that ample bobbin thread may be supplied thereon and unwinding of bobbin thread may be carried out smoothly and with time-wise relationship to stitching process regardless of the strong centrifugal force due to the rotation of rotary ring around the needle bar.
The above and further objects and novel features of the invention will be more fully appear from the following description when the same is read in connection with the accompanying drawings. It is to be expressly understood, however, that the drawing is for the purpose of illustration only and is not intended as a definition of the limits of the invention.